This application is based on Application No. 2000-318075, filed in Japan on Oct. 18, 2000, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention generally relates to an AC generator for use in a vehicle. More particularly, the present invention relates to a structure for connecting lead wires and neutral leads of a stator winding to a rectifier and also relates to a method for forming such a structure.
2. Description of the Related Art
FIG. 13 is a longitudinal sectional view illustrating a conventional AC generator for use in a vehicle. FIG. 14 is a perspective view illustrating a stator structure applied to the conventional AC generator. FIG. 15 is a perspective view of a primary part thereof and illustrates the connection between a metallic terminal and a conductor wire serving as a stator winding of a stator, which is applied to the conventional AC generator for use in a vehicle. FIG. 16 is a perspective view illustrating a mounting structure for mounting the stator winding of the conventional AC generator on a rectifier.
As shown in FIG. 13, the AC generator for use in a vehicle comprises a case 3 consisting of an aluminum front bracket 1 and an aluminum rear bracket 2, a shaft 6 having an end portion to which a pulley 4 is fixed, a Lundell type rotor fixed to this shaft 6, fans 5 respectively fixed at both axial end portions of this rotor 7, a stator 8 fixed to the cased 3 in such a way as to surround the rotor 7, slip rings 9, fixed to the other end portion of the shaft 6, for supplying an electric current to the rotor 7, a pair of brushes 10 adapted to slide over the surface of the slip rings 9, a brush holder 11 for accommodating the pair of brushes 10, a rectifier 12, electrically connected to the stator 8, for rectifying an alternating current generated in the stator 8 into a DC current, and a regulator 18, fitted into the brush holder 11, for regulating an AC voltage generated in the stator 8.
The rotor 7 has a field coil 13 adapted to generate magnetic flux when an electric current is fed thereto, and a pair of pole cores 20 and 21 provided in such a manner as to cover this field coil 13, magnetic poles being formed in the poles 20 and 21 by the magnetic flux. Further, the pair of pole cores 20 and 21 has iron claw-shaped magnetic poles provided with equal angular pitches in the direction of the circumference of the an outer peripheral portion thereof in such a way as to protrude therefrom so that the maximum radial section thereof is nearly trapezoidal. Moreover, the pair of pole cores 20 and 21 is securely fixed to the shaft 6 so that the claw-shaped magnetic poles 22 and 23 are made to face and mesh with each other.
The stator 8 is constituted by a cylindrical stator core 16 formed by using laminated magnetic steel plates and a stator winding 17 wound around the stator core 16, as illustrated in FIG. 14. A plurality of slots 16a each extending in an axial direction are formed with a predetermined pitch in the circumferential direction in the stator core 16. The stator winding 17 is constituted by three winding units 26 each obtained by winding a copper conductor wire 25 having a circular cross section coated with electrical insulation for a predetermined number of turns into a wave-shaped pattern. The three winding units 26 are wound around the stator core 16 in such a way as to be respectively accommodated in every three slots 16a by shifting each of the slots, in each of which the corresponding winding unit is accommodated, by one slot. The beginning end portions of the winding units 26 constitute lead wires 26a, 26b, and 26c, respectively. The finishing ends of the winding units 26 constitute neutral points 26n. Further, the stator winding 17 is constituted by bringing together the neutral points 26n of the three winding units 26, that is, establishing three phase alternating current connection (Y-connection) among the three winding units 26. Moreover, a metallic terminal 27 made of, for example, tough pitch copper is connected to each of the lead wires 26a, 26b, and 26c. Furthermore, one end portion of the neutral lead 28 and the three neutral points 26n are put together and integrated with one another by solder. Another metallic terminal 27 is connected to the other end portion of the neutral lead 28.
Incidentally, as shown in FIG. 15, the metallic terminal 27 is connected to the conductor wire 25 at a portion A by soldering or welding after the grasping piece 27a thereof is caulked and attached to the end portion, from which the insulating coating is removed, of the conductor wire 25. Additionally, the metallic terminal 27 is similarly connected to the other end portion of the neutral lead 28.
As illustrated in FIG. 16, the rectifier 12 comprises a plurality of positive-electrode-side diodes 30 and negative-electrode-side diodes 31 for performing full-wave rectification on three-phase alternating current, first and second cooling plates 32 and 33 for cooling the positive-electrode-side diodes 30 and the negative-electrode-side diodes 31, an insulator 34 for insulating the first and second cooling plates 32 and 33, a circuit board 35, and an output terminal 36.
The first cooling plate 32 is formed in a horseshoe shape. The positive-electrode-side diodes 30 are mounted on a principal surface 32a thereof in such a way as to be arranged in the direction of the circumference thereof Further, radiating fins 32b are erected on the rear surface (that is, the surface opposite to the principal surface) of the first cooling plate 32. Moreover, flange portions 32c radially and outwardly extend from both circumferentially end portions of and a central portion of the first cooling plate 32. Furthermore, a through hole (not shown) is dug in each of the flange portions 32c. 
The second cooling plate 33 is formed in a horseshoe shape in such a way as to have a diameter, which is larger than that of the first cooling plate 32. The negative-electrode-side diodes 31 are mounted on a principal surface 33a of second cooling plate 33 in such a manner as to be arranged in the direction of the circumference thereof. Moreover, through holes (not shown) are dug in both circumferential end portions of and a central portion of the second cooling plate 33 correspondingly to the through holes dug in the first cooling plate 32.
The circuit board 35 is a resin molding in which wiring for constructing diode bridges of the positive-electrode-side diodes 30 and the negative-electrode-side diodes 31 are insert-molded. Further, the circuit board 35 is formed in a horseshoe shape, similarly as the second cooling plate 33. Moreover, through holes 35a are dug in both circumferentially end portions of and a central portion of the circuit board 35 correspondingly to the through holes dug in the first cooling plate 32. Furthermore, screw holes 37a, 37b, 37c, and 37n for electrically connecting the lead wires 26a, 26b, and 26c and the neutral leads 28 of the stator winding 17 to the rectifier 12 are provided therein. Additionally, each of mounting seats 39a, 39b, 39c, and 39n is provided on the outer peripheral portion around a corresponding one of the screw holes 37a, 37b, 37c, and 37n. 
This rectifier 12 is assembled as follows. First, the first cooling plate 32 is placed so that the through hole dug in each of the flange portions 32c is aligned with a corresponding one of through holes dug in the second cooling plate 33. Moreover, the circuit board 35 is stacked on the cooling plate 32 so that each of the through holes 35a is aligned with a corresponding one of the through holes dug in the flange portions 32c. At that time, an insulator 34 is interposed between each of the flange portions 32c and the principal surface 33a of the second cooling plate 33. Thus, the electrical connection between each of the flange portions 32c and the principal surface 33a is prevented from being established. The first cooling plate 32 and the second cooling plate 33 are concentrically arranged so that the principal surfaces 32a and 33a are in the same plane position. The positive-electrode-side diodes 30 and the negative-electrode-side diodes 31 are disposed so that each of the diodes 30 faces a corresponding one of the diodes 31. Furthermore, a connecting terminal 35b extending from each of the mounting seats 39a, 39b, 39c, and 39n is put between each of the terminal 30a of the positive-electrode-side diodes 30 and a corresponding terminal 31a of the negative-electrode-side diodes 31 and connected thereto by solder. Subsequently, an output terminal 36 is passed through one of the through holes 35a formed in the circuit board 35 and the through holes dug in the first cooling plate 32 and the second cooling plate 33. Thus, the rectifier shown in FIG. 16 is assembled.
The rectifier 12 assembled in this manner is attached to the rear bracket 2 by passing mounting screws (not shown) through the remaining two through holes 35a and the through holes dug in the first cooling plate 32 and the second cooling plate 33 and screwed in screw holes (not shown) provided in the rear bracket 2.
Then, the lead wires 26a, 26b, and 26c and the neutral lead 28 of the stator winding 17 are electrically connected to the rectifier 12. Incidentally, as illustrated in FIG. 16, the metallic terminal 27 connected to the neutral lead 28 is put above the screw hole 37n. Then, a mounting screw 38 is passed through a hole 27b of the metallic terminal 27. Moreover, the screw 38 is screwed into the screw hole 37n. Thus, the metallic terminal 27 is electrically connected to the mounting seat 39n. Similarly, the metallic terminals 27 connected to the lead wires 26a, 26b, and 26c are electrically connected to the mounting seats 39a, 39b, and 39c by screwing the mounting screws 38 into the screw holes 37a, 37b, and 37c, respectively.
In the conventional AC generator for use in a vehicle, which is constructed as described above, electric current is supplied from a battery (not shown) to the field coil 13 through the brushes 10 and the slip rings 9. Thus, magnetic flux is generated therein. The claw-shaped magnetic poles 22 of the pole core 20 are magnetized into North-seeking (N) poles by the magnetic flux, while the claw-shaped magnetic poles 23 of the pole core 21 are magnetized into South-seeking (S) poles.
On the other hand, the pulley 4 is driven by an engine. The rotor 7 is rotated by the shaft 6. This rotation of the rotor 7 causes a rotating magnetic field in the stator core 16, so that an electromotive force is generated in the stator winding 17. Alternating current electromotive force generated in this stator 8 is rectified by the rectifier 12 to a DC current. Moreover, the magnitude of an output voltage thereof is adjusted by a regulator 18. Further, an output of the rectifier 12 is charged to the battery through the output terminal 36.
In the conventional AC generator for use in a vehicle, each of the lead wires 26a, 26b, and 26c and the neutral lead 28 thereof is connected to the metallic terminal 27. Thus, the conventional AC generator for use in a vehicle has drawbacks in that the number of components increases, that the number of man-hours needed for connecting the metallic terminals 27 increases, and that the cost thereof increases. In the case of this conventional generator, the number of slots per pole per phase is 1. When the number of slots per pole per phase increases, the number of the lead wires and the neutral leads also increases. This results in additional increase in the number of components and the number of man-hours needed for the connecting operation.
Furthermore, in the conventional generator, the connection between the stator winding 17 and the rectifier 12 is established by using the metallic terminals 27. Thus, the conventional generator has the following defects and a drawback in that the reliability thereof is degraded.
First, the strength of the connection from each of the lead wires 26a, 26b, and 26c, and the neutral lead 28 to the rectifier 12 depends upon that of the connection from each of the metallic terminal 27 to a corresponding one of the lead wires 26a, 26b, and 26c and the neutral lead 28.
Further, when the connection from each of the metallic terminal 27 to a corresponding one of the lead wires 26a, 26b, and 26c and the neutral lead 28 is established by using solder, problems of the heat resistance and life of the solder occur. That is, there is a fear that the thermal degradation of the connecting portion occurs and results in disconnection from the metallic terminal from the wires and the lead. Furthermore, when the solder is deteriorated, the connection resistance increases. This results in increase in the calorific value of heat generated in a portion whose connection resistance increases. Thus, the thermal degradation of the solder is accelerated. Furthermore, to solve such a problem, it has been considered that the heat resistance is increased by using lead solder. However, this causes an environmental problem. Moreover, an increase in the melting point results in degradation in the soldering workability thereof.
Further, when the metallic terminals 27 are welded to the lead wires 26a, 26b, and 26c, and the neutral lead 28, the melted and hardened portions of the conductor wires 25 are liable to crack. Moreover, when welded, oxides contained in the metallic terminals 27 and the conductor wires 25 are reduced, so that water vapor is generated. The generation of this water vapor causes intercrystalline cracks, so that blowholes are generated in the melted and hardened portions of the metallic terminals 27 and the conductor wires 25. This results in decrease in the connection strength and increase in the connection resistance. Consequently, there are fears that weld break occurs owing to the vibration of the generator, and that furthermore, a high temperature of the insulative coating 25a at the time of welding damages the coating 25a and results in corrosion of the conductor wires 25.
Additionally, in the case of connecting the conductor wires 25 to the metallic terminals 27 by caulking the grasping pieces 27a without soldering and welding, there are fears that the strength of the connection therebetween is unstable, and that the connection resistance increases. Besides, in the case that an excessive pressure is applied when the pieces 27a are caulked, the break of the metallic terminal 27 may occur.
In order to solve the above-mentioned problems, it is an object of the present invention to provide an AC generator for use in a vehicle, which eliminates the need for the metallic terminals by processing end portions of conductor wires and forming the connection latch portion for connecting each of the conductor wires to the rectifier, and which reduces the cost by decreasing the number of components and the number of man-hours needed for a connecting operation, and which enhances the reliability thereof.
Further, another object of the present invention is to provide a method for forming the connection latch portions, which are fastened to the mounting seats of the rectifier, with a low cost at the end portions of the conductor wires applied to the stator winding.
According to an aspect of the present invention, there is provided an AC generator (hereunder referred to as a first AC generator) for use in a vehicle, which has a stator having a stator core and a stator winding wound around the stator core, and a rectifier for rectifying an AC output of the stator. This AC generator further comprises a connection latch portion formed at an end portion of each of conductor wires constituting the stator winding in such a manner as to have a mounting hole. In this AC generator, the conductor wires are connected to the rectifier by passing mounting screws through the mounting holes to thereby fasten and fix the connection latch portions to mounting seats of the rectifier.
Further, in an embodiment (hereunder referred to as a second AC generator) of the first AC generator of the present invention, each of the connection latch portions is formed like a plate.
Further, in an embodiment (hereunder referred to as a third AC generator) of the second AC generator of the present invention, each of the connection latch portions is formed in such a manner as to have a thickness nearly equal to that of the conductor wires.
Further, in an embodiment (hereunder referred to as a fourth AC generator) of the first AC generator of the present invention, each of the connection latch portions is formed by folding back the end portion of each of the conductor wires deformed like thin plates.
Further, in an embodiment (hereunder referred to as a fifth AC generator) of the first AC generator of the present invention, each of the conductor wires has a rectangular cross section. Each of the connection latch portions is formed by digging the mounting hole in the end portion of each of the conductor wires.
Further, in an embodiment (hereunder referred to as a sixth AC generator) of the fifth AC generator of the present invention, each of the connection latch portions is formed like a plate whose thickness is less than that of the conductor wires.
Further, according to another aspect of the present invention, there is provided a method for forming connection latch portions of conductor wires applied to a stator winding of an AC generator for use in a vehicle, which comprises the steps of removing an insulating coating from a predetermined end-side range of each of the conductor wires each covered with the insulating coating, deforming an end portion of each of the conductor wires like a plate, and forming a mounting hole in the end portion, which is deformed like a plate, of each of the conductor wires.
Moreover, according to another aspect of the present invention, there is provided a method for forming connection latch portions of conductor wires applied to a stator winding of an AC generator for use in a vehicle, which comprises the steps of removing an insulating coating from a predetermined end-side range of each of the conductor wires each covered with the insulating coating, bending an end portion of each of the conductor wires like a ring, and deforming the end portion, which is bent like a ring, of each of the conductor wires like a plate and subsequently forming a mounting hole in the end portion of each of the conductor wires.
Furthermore, according to another aspect of the present invention, there is provided a method for forming connection latch portions of conductor wires applied to a stator winding of an AC generator for use in a vehicle, which comprises the steps of removing an insulating coating from a predetermined end-side range of each of the conductor wires each covered with the insulating coating, deforming an end portion of each of the conductor wires like a sphere by melting the end portion thereof, deforming the end portion, which is deformed like a sphere, of each of the conductor wires like a plate, and forming a mounting hole in the end portion of each of the conductor wires.